Molten Lava Cakes

My son has requested molten chocolate lava cakes for his birthday dessert (11 years old, how did that happen!). Those individual cakes that you cut into and all the chocolaty oozy stuff oozes onto your plate. Every time I have tried to make these, either it's all ooze or more often, little dry, bitter hockey pucks. Every cheesey restaurant chain on the planet can make these, why can't I? Any double secret tips you can give me will be appreciated. Thank you.